Glossary · Conversation
What is tool calling in a voice agent?
Tool calling in voice agents
Tool calling lets a voice agent reach your systems during a conversation, such as checking an order or booking a slot. The model decides when it needs a tool, asks for it with the right inputs, and uses the answer in its reply.
On a call
Caller: "मेरा parcel कहाँ है?" The agent calls your order-status API with the phone number it already has, gets "out for delivery", and says "आज शाम तक पहुँच जाएगा" without putting the caller on hold.
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Explained
Here is how it works, in plain words.
Without tools, an agent can only talk about what’s in its prompt. Tools let it check an order or book a slot while the caller is still on the line.
Under the hood it’s the same function calling that chat models use. You describe each tool to the model: a name, what it does, and the inputs it needs. During the conversation the model can reply with words, or with a request to run a tool. The tool runs, and its result goes back to the model, which then speaks.
Voice makes this harder in two ways. The first is time. A caller notices a two-second silence, so a slow tool needs cover. The agent can say “एक second, check कर रही हूँ” while it waits, or the tool can run in the background while the conversation carries on.
The second is inputs. A chat user types an order number. A caller says it, and the recogniser may drop a digit. Good agents read the value back before they use it, especially for anything that books, cancels or charges.
It helps to split tools by when they run. Some belong before the call: look up the customer, so the greeting uses their name. Some belong in the call: check stock, book a slot. And some belong after it, like writing the outcome to your CRM, where nobody is waiting.
Be careful what the prompt promises. If no tool sends a payment link, the agent shouldn’t say “I’m sending the link now”. Have it say the team will follow up instead.
In Frequency
This is what Frequency does about it.
Tools run before a call to fetch context, during it when the agent decides it needs one, and after it to send the outcome to your CRM. An on-call tool can make the agent wait for the answer, or run in the background and hand the result back when it's ready. Secrets stay in the workspace and never come back to the editor.